For the use as a repellent for harmful animals such as rats, birds or other pests, ultrasonic generators using piezoelectric elements are known. For example, the ultrasonic waves of 20 kHz or higher are used for repelling harmful animals.
In particular, such conventional ultrasonic generators that generate ultrasonic waves with high output to widen a region being affected are disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-165923 (published on Jun. 22, 2006) “Piezoelectric ultrasonic vibrator”, Korean Utility Model Registration No. 20-0409300 (published on Feb. 24, 2006) “Ultrasonic washer for vibrator structure”, and the present applicant's Korean Patent No. 10-1505410 (published on May 25, 2015) “Ultrasonic generator for pest repeller”.
Such conventional arts generally have a structure in which an ultrasonic wave generating body such as a piezoelectric element generating ultrasonic waves is attached to a diaphragm which receives and transmits the ultrasonic waves to emit the ultrasonic waves therefrom.
However, the above structure has a drawback that the joint portion between the ultrasonic wave generating body and the diaphragm is easily separated or broken due to the increased vibration impact to shorten a useful life of an ultrasonic generator. Also in the diaphragm, which is in the form of a speaker horn being connected to the ultrasonic wave generating body through an elongate connecting rod, the amplitude of the vibration generated by the ultrasonic waves is increased as the vibration moves toward the outer edge of the diaphragm, which causes an outer edge of the diaphragm to be cracked or ruptured after a long use, so that the effect of the ultrasonic waves generated for repelling harmful animals may be degraded.